Method and apparatus for securing a connector to a coaxial cable

ABSTRACT

A method and apparatus for securing a connector to a coaxial cable, and in particular to a multilayer core coaxial cable, without causing any damage or disturbance to the core. A split ferrule is fitted together over an exposed portion of the core at the end of the cable and is then pushed back with a sleeve formed on the rear of the ferrule being forced between the cable core and outer conductor. When the ferrule is in place, it is secured to the cable by suitable means, such as crimping, and the forward portion of the ferrule is utilized to secure the ferrule, and thus the cable, to a connector body.

United States Patent [72] Inventors Norbert Joseph Sladek ReferencesCited UNITED STATES PATENTS z h ii Treschnm Norwalk, both of 1,324,99412/1919 Benjamin 339/208 3 089 115 5/1963 Wicks 339/177 7 0 as 21 19693,295,076 12/1966 Kraus 333/97 Patented Sew 25,1971 3,349,166 10/1967Ziegler 174/88 3,363 221 1/1968 Stark 339/177 [73] Assignee TheBunker-Ramo Corporation oak Brook, I". 3,441,659 4/1969 Laudig et a1.174/88 Primary Examiner-Stephen J. Novosad Assistant Examiner-LawrenceJ. Staab Attorney-Frederick M. Arbuckle [54] METHOD AND APPARATUS 2SEEURING A ABSTRACT: A method and apparatus for securing aconneccoNiqEc'goR To AFOAXIAL tor to a coaxial cable, and in particularto a multilayer core 1 ch 3 "wing coaxial cable, without causing anydamage or disturbance to [52] U.S. Cl 339/177 E, he c e A split ferruleis fitted together over an exposed por- 339/276 T, 174/89 tion of thecore at the end of the cable and is then pushed back [51] Int. Cl ..H0lr17/04, with a sleeve formed on the rear of the ferrule being forced H015/10 between the cable core and outer conductor. When the ferrule Fieldof Search 174/89, is in pl ce, it is secure to the cable by s it bl me ns h s 75.2, 88.2; 339/ C, 89 C, 90 C, 177 R, 177 E, 276 R, 276 D, 276 F,276 T, 208

'IIIIIIIIullnll'lllllllll crimping, and the forward portion of theferrule is utilized to secure the ferrule, and thus the cable, to aconnector body.

WIIIIIIIIIIIIIIIIIIIIIIIIIIIA 1 I METHOD AND APPARATUS FOR SECURING ACONNECTOR TO A COAXIAL CABLE This invention relates to a method andapparatus for securing a connector to a coaxial cable, and moreparticularly to a split ferrule which may be utilized to effect such aconnection to a multilayer core coaxial cable without causing fraying orother damage to the dielectric cable core.

In most applications where a connector is secured to a coaxial cable, acylindrical ferrule having an elongated shoulder is placed over the endof the cable and the shoulder is forced back between the cable core andthe outer conductor of the cable. The cable is then secured to theferrule by crimping or other means and the forward end of the ferrule isutilized to secure the cable to a connector body.

With standard coaxial cables using extended polyethylene and Teflondielectrics, this procedure causes no problems. However, standard cablesare only moderately flexible and, in applications where a highlyflexible cable is required, a mu]- tilayer core isemployed. When atight-fitting ferrule is forced over the end of such a cable core, itgenerally picks up the end of the core, causing portion of the core tobe pushed back. With large cables and connectors, this is not a seriousproblem. However, with small, precision coaxial connectors, where VSWRis critical, such disturbance to the cable core cannot be tolerated.

It is, therefore, a primary object of this invention to provide a methodand apparatus for securing a connector to a multilayer core coaxialcable without causing any damage or disturbance to the core.

A more specific object of this invention is to provide a ferrule whichmay be used in conjunction with cables having a multilayer core withoutcausing damage or disturbance to the cable which would adversely effectVSWR.

In accordance with these objects, this invention provides a ferrulewhich is fonned by fitting together at least two ferrule segments. Thesesegments may be fitted together over an exposed cable core at the end ofthe cable to form a ferrule having an enlarged cylindrical portion andan elongated cylindrical sleeve of smaller diameter concentrictherewith. The sleeve ends in a tapered surface which is adapted to fitunder the outer conductor of the cable. Since the ferrule is already ina position over the cable core before any sliding occurs, it does notcause dielectric bunching and other distortion to the dielectric whichoccurs when attempting to thread the dielectn'c through the bore of aone-piece ferrule. Means for aligning the segments are provided so thatthey may be properly fitted together. The end of the ferrule adjacentthe enlarged portion forms a flat surface perpendicular to the axis ofthe ferrule which surface may be utilized as a trimming jig for thecable core when the ferrule is properly positioned.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of a preferred embodiment of the invention, as illustratedin the accompanying drawings.

In the drawings:

FIG. 1 is a cutaway diagram of an assembled connector and cableutilizing the teachings of this invention.

FIG. 2 is a cutaway side view of a pair of ferrule segments suitable foruse in a preferred embodiment of the invention.

FIG. 3 is a front view of the ferrule segments shown in FIG. 2

Referring now to FIG. 1 it is seen that coaxial cable is formed of aninner conductor 12, a multilayer insulating core 14, a braided outerconductor 16, and an insulating outer cover 18. In securing cable 10 toa connector body 19, outer conductor 16 is first cut back a shortdistance from the end of the cable, the distance being about an inch butnot being critical, and outer cover 18 is then cut back by an additionaldistance of about an inch from outer conductor 16. A bushing 20 of ametallic conducting material, a crimp ferrule 22 of a similar material,and a coupling ring or collar 24, which is also of a metallic material,are then slipped in succession over the end of cable 10. Collar 24 hasan internally threaded ring 26 projecting therefrom.

A ferrule 28 of a metallic conducting material, such as brass, is thenfitted over the exposed portion of cable core 14. FIGs. 2 and 3 showferrule 28 in more detail. From these FIGS. it is seen that ferrule 28is formed of two like segments 28A and 283. Each of these segmentsincludes an enlarged semicylindrical portion 30, and an elongated sleeve32. The end of portion 30 has a short 45 angle chamfer 34 and a flatsurface 36 the function of which will be described shortly. The rearcomers of portion 30 are also chamferred. Each sleeve 32 has a ridgedsurface 38 and ends in a surface which tapers at a slight angle such as,for example, 15. The mating surface of the segments of ferrule 28 havesemicircular indentations which combine, when the segments are fittedtogether, to form an internal bore 42 having a diameter approximatelyequal to the diameter of multilayer core 14. A pair of aligning pins 44are fitted and secured in a mating pair of openings in one of thesegments and, when the segments are properly aligned, fit into a pair ofopenings 46 in the other of said segments. The pins 44 and openings 46may thus be used to align the two segments when they are being fittedtogether. Portions 30 also have a slot 48 formed around their outersurface. The function of slot 48 will be described shortly.

Referring again to FIG. 1, the segments of ferrule 28 are fittedtogether with sleeve portions 32 over core 14. Damage to the core whichwould occur when attempting to thread the core through the bore of aone-piece ferrule is thus avoided. The mated segments are then slid backalong the core with sleeve 32 being wedged between the core and braidedouter conductor 16. The tapered surface 40 of the sleeve assists in thiswedging action. When the ferrule is positioned as shown in FIG. 1, withthe cutback end of outer conductor 16 abutting the shoulder betweenportion 30 and sleeve 32, a snapring 50 is fitted into slot 48 to holdthe segments of ferrule 28 together. The flat surface 36 of the ferrulemay then be utilized as a trimming jig for cutting cable core 14. Thisexposes a short portion of inner conductor 12.

Collar 24 may then be slid back over outer conductor 16 into theposition shown in FIG. 1 in abutment with the shoulder between portions30 and 32 of ferrule 28. Ferrule 22, with bushing 20 wedged in it, isthen slid up over conductor 16 into position adjacent to collar 24,clamping the braided outer conductor 16 between bushing 20 and ferrule28. The connection of cable 10 to ferrule 28 is completed by crimpingferrule 22 with a crimp tool in a standard fashion. The ridges 38 onshoulder 32 coact with outer conductor 16 to provide a more secureconnection.

The elements of connector 19 which are now to be described, and theirmanner of connection, do not form part of the present invention, but arepresented for illustrative purposes only. Other elements adapted toperform the desired function could be utilized in their place.

A dielectric washer 51 is then placed over the center conductor l2abutting the surface 36, and a contact 52 is secured to the exposed endof conductor 12. This may be effected by, for example, sliding conductor12 into an internal bore in contact 52 and securing the contact to theconductor by a drop of solder in solder port 54. A connector body 56having an externally threaded ring projection 58 may then be fitted overcontact 52 and secured to cable 10 and ferrule 28 by screwing togetherthe threads on rings 26 and 58. Body 56 has an internal bore 60 with aninsulating sleeve 62 seated in a counterbore thereof. A coupling nut 64secured to body 56 by slipring 66 may be utilized to connect the contactassembly shown to a mating contact assembly.

A split ferrule design has thus been disclosed which enables a ferruleutilized to secure a coaxial cable to a connector to be fitted on thecable, without damaging a multilayer cable core. The shape of theferrule, and its relative dimensions would, of course, vary with thespecific connector application, and other equivalent elements may beutilized in place of pins 44 for aligning the ferrule segments. Further,while for most applications there is no need to divide ferrule 28 intomore than two segments, a ferrule formed of three or more matingsegments is within the contemplation of the invention.

While the invention has been particularly shown and described withreference to a preferred embodiment thereof, it will be apparent tothose skilled in the art that the foregoing and other changes in formand details may be made therein without departing from the spirit andscope of the invention.

What is claimed is: i

l. A method of securing a connector to a multilayer core coaxial cablehaving an inner and an outer conductor comprising the steps of:

sliding a cylindrical crimp ferrule and a cylindrical connector memberonto said cable, said connector member having a cylindrical bore ofdiameter slightly larger than that of said cable and an enlargedcounter-bore;

trimming a predetermined amount of said outer conductor from the end ofsaid cable;

fitting the segments of a split ferrule together over the exposed end ofsaid cable core, said ferrule, when fitted together, having an enlargedcylindrical portion, an elongated cylindrical sleeve of smaller diameterconcentric with said enlarged portion, and a flat surface formedperpendicular to the axis of said ferrule on the enlarged portion endthereof;

sliding said fitted-together ferrule up said core with said sleeve beingforced between said core and said outer conductor;

moving said connection member into engagement with said fitted-togetherferrule with at least a portion of said enlarged portion fitted in saidcounterbore, and securing said member, and thus also said ferrule, to amating connector body;

crimping said crimp ferrule over the portion of said outer conductorwhich is over said ferrule sleeve; and

utilizing the flat, enlarged portion end of said split ferrule, when itssleeve is properly positioned between said outer conductor and saidcore, as a trimming jig for trimming said core.

1. A method of securing a connector to a multilayer core coaxial cable having an inner and an outer conductor comprising the steps of: sliding a cylindrical crimp ferrule and a cylindrical connector member onto said cable, said connector member having a cylindrical bore of diameter slightly larger than that of said cable and an enlarged counterbore; trimming a predetermined amount of said outer conductor from the end of said cable; fitting the segments of a split ferrule together over the exposed end of said cable core, said ferrule, when fitted together, having an enlarged cylindrical portion, an elongated cylindrical sleeve of smaller diameter concentric with said enlarged portion, and a flat surface formed perpendicular to the axis of said ferrule on the enlarged portion end thereof; sliding said fitted-together ferrule up said core with said sleeve being forced between said core and said outer conductor; moving said connection member into engagement with said fitted-together ferrule with at least a portion of said enlarged portion fitted in said counterbore, and securing said member, and thus also said ferrule, to a mating connector body; crimping said crimp ferrule over the portion of said outer conductor which is over said ferrule sleeve; and utilizing the flat, enlarged portion end of said split ferrule, when its sleeve is properly positioned between said outer conductor and said core, as a trimming jig for trimming said core. 